Contactless switching apparatus

ABSTRACT

This contactless switching apparatus is comprised of a magnetic path having a U-shaped base of magnetic material, both ends whereof are made free, and a movable yoke which is put on one free end of the said base so that the inner end of the movable yoke can move inside both ends of the base, the said movable yoke being arranged so that the moving inner end of the said movable yoke may be opposite to the other free end of the said base to form a gap, either or both the movable yoke and one magnetic yoke of the base forming the said gap which are opposite to each other being made a bimetal yoke or bimetal yokes so that they bend in such a direction that the said gap may be narrowed when the base rises in temperature, a magneto-electric converting device being inserted in the said magnetic path so as to be actuated by the magnetic flux flowing in the magnetic path, and the converting device being connected to an external input power source and an external load.

United States Patent Kobayashi 51 May 2,1972

' s11 Int.Cl

[54] CONTACTLE SS SWITCHING APPARATUS I [72] Inventor: Tunekazu Kobayashi, Kawaski, Japan [73] Assignee: Denki Onkyo Co., Ltd., Tokyo, Japan [22] Filed: Sept. 8, 1970 [21] Appl. No.: 70,361

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 3.537.046 10/1970 Hubrich et al. ..32'3/94 H x Primary E.\'aminer C. L. Albritton v Attorney.lames E. Armstrong and Ronald S. Cornell [5 7] ABSTRACT This contaetless switching apparatus is comprised of a magnetic path having a U-shaped base of magnetic material, both ends whereof are made free, and a movable yoke which is put on one free end of the said base so that the inner end of the movable yoke can move inside both ends of the base, the said movable yoke being arranged so that the moving inner end of the said movable yoke may be opposite to the other free end of the said base to form a gap, either or both the movable yoke and one magnetic yoke of the base forming the said gap which are opposite to each other being made a bimetal yoke or bimetal yokes so that they bend in such a direction that the said gap may be narrowed when the base rises in temperature, a magneto-electric converting device being inserted in the said magnetic path so as to be actuated by the magnetic flux flowing in the magnetic path, and the converting device being connected to an external input power source and an external load.

7 Claims, Drawing Figures PATENTEDMM 2|912 3. 660,795 sum 1 or 2 BACKGROUND OF THE INVENTION The present invention relates to a contactless switching apparatus using a magneto-electric converting device (hereinafter referred to as the converting device") such as a Hall efiect device, a magneto-resistance device, etc.

The known switching apparatus of the type described are so structured that they are equipped with a movable yoke on the end of one magnetic yoke of a U-shaped base, providing a gap between the moving end of the movable yoke and the end of the other magnetic yoke of the base, the yoke in relation to the gap being equipped with a converting device in the gap. In this type of known switching devices, the gap is varied in distance by moving the movable yoke to change the magnetic flux applied to the converting device.

However, the switching apparatus heretofore used have the disadvantage that a temperature compensating means is required for use in high accuracy equipment because the converting device largely depends on temperature. Moreover, the temperature compensating means has the disadvantage that the circuit thereof was complicated and expensive because a temperature compensating device such as a posistor or a thermistor is used in the circuit to compensate resistance change inthe converting device caused by temperature, or because the said temperature compensating device, the re sistance of which changes with the ambient temperature,'is inserted in a part of the feedback circuit of an amplifier system connected to the converting device. In the case when the converting device is fitted on a material which provides a large heat capacity, the temperature compensating means has the disadvantage that the response characteristic of the converting device to the ambient temperature becomes worse. In the case the temperature difference between the converting device and the temperature compensating device is not uniform, the temperature compensating means has the disadvantage that accurate temperature compensation is difficult to obtain.

The object of the present invention is to provide a contactless switching apparatus capable of efficiently achieving temperature compensation and which at the same time is simple in structure and low in manufacturing cost.

SUMMARY In accordance with the invention there is a contactless switching apparatus comprised of a magnetic path having a U- shaped base of magnetic material, both ends of which are made free, and a movable yoke which is put on the free end of one magnetic yoke of the said base so that the inner end of the said movable yoke is placed opposite to the free end of the other magnetic yoke, and of a converting device such as a Hall effect device, or a magneto-resistance device which is inserted in the said magnetic path so as toreceive the magnetic flux flowing therethrough, and of a driving means which actuates the said movable yoke in such a manner that the inner end of the said movable yoke can approach to and separate from a particular point of the magnetic yoke faced to the inner end; the said movable yoke and the magnetic yoke faced to the inner end thereof forming a gap, the distance of the said gap being changed by moving or sliding the said movable yoke, either or both the movable yoke and the magnetic yoke of the said base forming the said gap being made a bimetal yoke or bimetal yokes so as to bend in the direction in which the gap is narrowed when the base increases in temperature, and the said converting device being connected with an external input power supply and with an external load.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in detail in the accompanying drawings in which: v

' FIG. 1 is a front view of the switching apparatus according to the present invention.

FIG. 2 is a front view showing another embodiment of the switching apparatus according to the present invention.

FIGS. 3a and 3b are enlarged views showing parts of the bimetal yoke of the switching apparatus according to the present invention, respectively.

FIG. 4 is a circuit diagram showing the magnetic circuit of theswitching apparatus illustrated in FIG. 1.

FIGS. 5, 6, and 7 are front views showing other embodiments of the switching apparatus according to the present invention, respectively.

DETAILED DESCRIPTION Referring to FIG. I of the drawings, the switching apparatus according to the present invention comprised. of a magnetic path 10 which composes a U-shaped base 11 of magnetic material and a movable yoke 12 which is put on the free end of one magnetic yoke 11a of the said base so as to move on the said freeend of magnetic yoke 11a as a fulcrum, a converting device '20 which is inserted in magnetic path 10 so as to be actuated by the magnetic flux flowingin the said magnetic path, an external input power supply 30 which is connected to the said converting device, an external load 40 which is connected to the said converting device, and a bimetal strip 50 which is fitted on a magnetic yoke 11b on which movable yoke 12 is not placed and is opposite to magnetic yoke 11a of base 11.

Base 11 is comprised of a bottom plate 11c which is made of a permanent magnet or an electromagnet, and is comprised'of two magnetic yoke lland 11b which are mounted on bottom plate 11c at the both magnetic poles N and S thereof, respectively, and are arranged in parallel with each other.

As depicted above, base 11 has the permanent magnet at the center of the said magnetic base as usual. According to circumstances, two magnetic yokes 11a and 11b or movable yoke 12 may be made permanently magnetic; otherwise, a permanent magnet or an electromagnet may be placed outside the said baseas the magnetic flux generating means.

However, itis necessary to avoid a bimetal yoke made of a permanent magnet, because the material of the bimetal yoke provided between the said magnetic yoke and the movable yoke cannot use a ferrite. Movable yoke 12 is put on one magnetic yoke 11a of base 11 so as to move on the free end of magnetic yoke 11a as the fulcrum.

Inner end 12a of movable yoke 12 is placed opposite to the other magnetic yoke 11b of base 11 so as to form a gap G, and outer end 12b of movable yoke 12 is extended to the outside of base 11, being devised so as to be moved to up and down by actuating means 60.

Since movable yoke 12 is attracted to magnetic'yoke 11a, other separate coupling means is not required.

It is necessary for movable yoke 12 to fix the inner end thereof by-ascending, or by descending, when outer end 12b is not pressed by actuating means 60; that is, when outer end 12b is in the released steady state.

In order to lower the said inner end in the steady state, as illustrated in FIG. 1, the inner end side to the fulcrum of movable yoke 12 may be made heavier than the outer end side so that the inner end can descend by the empty weight thereof. In this case, in order to determine the lowered position of the inner end of movable yoke 12, it is desirable to provide a stopper 13 at the falling position.

Also, in order to fix the inner end of movable yoke 12 on the raised position in the steady state, the outer end of the movable yoke may be made heavier than the inner end. In this case, however, it is rather desirable to fix and move the movable yoke by the use of the actuating means 60, as illustrated in FIG. 2.

A variety of methods for using the said actuating means are available; however, in many cases, a push-button cap 60 mounted over magnetic path 10 is used to depress and release outer end 12b of the movable yoke in such a manner that a protruding part 61 fitted on the inside wall of push-button cap 60 may press on outerend 12b, as illustrated in FIG. 1.

' Push-button cap 60, of course, is also available for the switching apparatus illustrated in FIG. 2. In this case, the push-button cap is provided with a protrusion inside it, the

protrusion depressing the portion inside the fulcrum of movable yoke 12.

Converting device 20 is provided on magnetic yoke 11b of base 11 opposite to the inner end of movable 12 in such a position that the magnetic flux flowing through magnetic path can be applied to converting device 20 when movable yoke 12 moves to approach the inner end thereof to converting device 20, that is, movable yoke 12 is on the descended position thereof according to FIG. 1.

As converting device 20, either a Hall effect device or a magneto-resistance device may be used. When the Hall effect device is used, a magnetic flux is applied to the Hall effect device to generate a Hall voltage, so that a cutting-off operation resulting from the voltage increase in the device can be obtained. When the magneto-resistance device is used, a magnetic flux is applied to the said device to increase the internal resistance thereof, so that the cutting-off operation resulting from the current drop down in the device can be obtained.

While an active element such as a transistor, a vacuum tube, or a SCR is generally used as load 40, it is particularly understood that the load is not limited thereto but other detecting loads can be used.

Bimetal strip 50 is provided on magnetic yoke 11b forming gap G; therefore, magnetic yoke 11b is made a bimetal yoke.

Bimetal yoke 1 lb is devised so as to bend in the direction of inner end 12a of movable yoke 12 when the temperature of the said magnetic path increases; therefore, gap G becomes narrower when the temperature increases.

Bimetal yoke 11b may be composed of a bimetal strip 50 which is devised by jointing two metallic strips 51 with each other, asillustrated in FIG. 3a; or, bimetal yoke 11b and the other bimetal strip 50' mounted thereon may be used as the bimetal, as illustrated in FIG. 3b.

As will be understood from the above explanation, the switching apparatus according to the invention can perform a switching operation by the change of the output voltage of the converting device and the output current thereof. The change is caused by moving movable yoke 12 to bring the inner end thereof near to or far away from converting device 20.

In the case when magnetic path 10 increases in temperature, the internal resistance of converting device 20 decreases; however, bimetal yoke 11b used in the switching apparatus bends to approach converting device 20 to movable yoke 12, thus resulting in increase of the magnetic flux applied to converting device 20. Therefore, in the switching apparatus according to the invention, a resistance decrease or an output decrease caused in converting device 20 by a temperature change is compensated by increase of the magnetic flux.

Referring to FIG. 2, there is shown a switching apparatus composed of movable yoke 12 being a bimetal yoke. According to the embodiment mentioned above, movable yoke 12 bends with temperature, so that the size of gap G formed between converting device 20 and the inner end 12a of movable yoke 12 can be made narrow when the temperature of the magnetic path increases. Use of any switching apparatus according to the embodiments stated heretofore provides the following advantages.

.The temperature characteristic of the converting device and the temperature characteristic of the permanent magnet of the apparatus can be compensated by choosing the proper'bimetal strip as to material, thickness, and size and by choosing the proper bimetal yoke for size; therefore, the design of various parts of the switching apparatus and the manufacture thereof can be made easy and accordingly is not expensive. Since converting device 20 and the magnetic path can be considered identical in temperature, a particularly good response characteristic of the magnetic path to the temperature change thereof can be obtained. Especially, by mounting the converting device on the bimetal yoke, as illustrated in FIG. 1, an extremely good compensating effect to the temperature change is obtained.

Comparing with a prior art switching apparatus using a compensating device such as a thermistor and the like, the

switching apparatus according to the invention is advantageous in power loss and operation reliability because the output change of the converting device can directly act on the load without affecting from the compensating device.

FIGS. 5, 6, and 7 show switching devices in each of which a magnetic flux adjusting block 70 made of magnetic material is provided in magnetic path 10 so as to'befreely attachable and separable. By attaching magnetic flux adjusting block 70 on magnetic path 10 through a bimetal 80, the magnetic flux flowing in magnetic path 10 is increased when the temperature thereof increases.

As is illustrated in FIGS. 5 and 6, a permanent magnet is used as magnetic flux adjusting block 70 in normal cases; however, according to circumstances, a non-magnetized block of magnetic material as is illustrated in FIG. 7 may be used, or an electromagnet may be also used.

In each embodiment shown in FIGS. 5 and 6, magnetic flux adjusting block 70, made of a permanent magnet, is placed on base plate 11C of the permanent magnet of base 11.

In the embodiment shown in FIG. 5, base plate 11C and magnetic flux adjusting block 70 are so positioned in parallel that the poles of opposite polarity are facing each other. When the temperature increases, bimetal bends to separate magnetic flux adjusting block 70 far away from the magnetic path.

According to the above-mentioned embodiment, by

separating magnetic flux adjusting block 70 far away from the magnetic path, the magnetic flux flowing through magnetic flux adjusting block 70 is reduced, so that the magnetic flux flowing in the magnetic path can be increased.

In the embodiment shown in FIG. 6, base plate 11C and magnetic flux adjusting block 70 are so positioned in parallel that the poles of the same polarity are facing each other. When the temperature increases, bimetal 80 bends to approach or touch magnetic flux adjusting block 70 to magnetic path 10. According to the embodiment described above, when the temperature increases, the magnetic flux flowing in magnetic flux adjusting block 70 changes to flow through the magnetic path, so that the magnetic flux netic path can be increased.

In the embodiment shown in FIG. 7, magnetic flux adjusting block 70, made of non-magnetized magnetic material, is constructed so as to be attached to or separated from base plate 1 1C. When the temperature increases, magnetic flux adjusting block 70 is separated from magnetic path 10 to increase the magnetic flux of magnetic path 10.

Movable yoke 12 employed in each of the embodiments described above may be made either a tilt type as shown in FIG. 1 or a slide type as shown in FIG. 7. I

In each of the embodiments shownin FIGS. 5 through 7, in order to provide a restriction to the attaching or the separating direction of magnetic flux block 70, it is desirable to place sliding guides and 90 as illustrated in FIG. 7. Converting device 20 is usually positioned in the gap; however, the converting device can be fitted at any position in the magnetic path, in the case that the size of gap G is largely changed by movement of movable yoke 12, resulting in great change of the magnetic resistance of magnetic path 10, as will be understood from FIG. 7.

In each of the embodiments shown in FIGS. 5 through 7, when the temperature increases, the bimetal yoke bends and, at the same time, magnetic flux adjusting block 70 increases the magnetic flux in magnetic path 10; therefore, successful compensations can be obtained against the resistance decrease of converting device 20 and against the output decrease thereof when the temperature increase occurs.

What is claimed is:

l. A contactless switching apparatus which comprises a. means creating a magnetic path said means including a U- shaped base of magnetic material wherein the two legs of said U constitute first and second magnetic yokes and a third yoke which is movably mounted on the free end of the first magnetic yoke of the said base so that the inner end of the movable yoke is positioned adjacent to the end of the second magnetic yoke,

flowing through the magb. a converting device inserted in the magnetic path so as to receive the magnetic fluxflowing therein,

c. an external input power supply and an external load operatively connected to said converting device,'and

d. drive means for actuating said movable yoke in such a mannerthat the inner end of said third yoke can approach to and separate from a particular point of said second magnetic yoke, said third yoke and said second magnetic yoke forming a gap therebetween, the size of said gap being changed by movement of said third yoke, at least one of said second and third yokes being bimetallic whereby said gap is narrowed when the temperature of the magnetic path increases.

2. A contactless switching apparatus according to claim 1, wherein said second yoke is bimetallic and said converting device is mounted on the surface of the bimetallic yoke.

3. A contactless switching apparatus according to claim 1, wherein the said third yoke is slidably mounted on said first yoke.

4. A contactless switching apparatus according to claim l,'

wherein a magnetic flux adjusting block made of magnetizable material is mounted in the magnetic field, and a bimetallic means movably mounts said magnetic flux adjusting block whereby said block can be moved towards and away from said magnetic field to increase the magnetic flux density in the magnetic path when the temperature increases.

5. A contactless switching device according to claim 4, including a bottom plate formed on the center portion of said U- shaped base is a magnet, the magnetic flux adjusting block comprises a magnet attached on the said base plate in parallel relation thereto so that the polarities of the poles of said magnetic flux adjusting block and the base plate facing each other are opposite and wherein said magnetic flux adjusting block becomes separated from the base plate by said bimetallic means when the temperature increases.

6. A contactless switching device according to claim 4, including a bottom plate formed on the center portion of said U- shaped base is a magnet, the magnetic flux adjusting block comprises a magnet attached on the said base plate in parallel relation thereto so that the polarities of the poles of said magnetic flux adjusting block and the base plate facing each other are the same, and whereing said magnetic flux adjusting block becomes closer to the base plate by said bimetallic means when the temperature increases.

7. A contactless switching device according to claim 4, including a bottom plate formed on the center portion of said U shaped base is a magnet, the magnetic flux adjusting block comprises a non-magnetized, magnetic material attached on the said base plate, and said magnetic flux adjusting block becomes separated from the base plate by said bimetallic means when the temperature increases. 

1. A contactless switching apparatus which comprises a. means creating a magnetic path said means including a Ushaped base of magnetic material wherein the two legs of said U constitute first and second magnetic yokes and a third yoke which is movably mounted on the free end of the first magnetic yoke of the said base so that the inner end of the movable yoke is positioned adjacent to the end of the second magnetic yoke, b. a converting device inserted in the magnetic path so as to receive the magnetic flux flowing therein, c. an external input power supply and an external load operatively connected to said converting device, and d. drive means for actuating said movable yoke in such a manner that the inner end of said third yoke can approach to and separate from a particular point of said second magnetic yoke, said third yoke and said second magnetic yoke forming a gap therebetween, the size of said gap being changed by movement of said third yoke, at least one of said second and third yokes being bimetallic whereby said gap is narrowed when the temperature of the magnetic path increases.
 2. A contactless switching apparatus according to claim 1, wherein said second yoke is bimetallic and said converting device is mounted on the surface of the bimetallic yoke.
 3. A contactless switching apparatus according to claim 1, wherein the said third yoke is slidably mounted on said first yoke.
 4. A contactless switching apparatus according to claim 1, wherein a magnetic flux adjusting block made of magnetizable material is mounted in the magnetic field, and a bimetallic means movably mounts said magnetic flux adjusting block whereby said block can be moved towards and away from said magnetic field to increase the magnetic flux density in the magnetic path when the temperature increases.
 5. A contactless switching device according to claim 4, including a bottom plate formed on the center portion of said U-shaped base is a magnet, the magnetic flux adjusting block comprises a magnet attached on the said base plate in parallel relation thereto so that the polarities of the poles of said magnetic flux adjusting block and the base plate facing each other are opposite and wherein said magnetic flux adjusting block becomes separated from the base plate by said bimetallic means when the temperature increases.
 6. A contactless switching device according to claim 4, including a bottom plate formed on the center portion of said U-shaped base is a magnet, the magnetic flux adjusting block comprises a magnet attached on the said base plate in parallel relation thereto so that the polarities of the poles of said magnetic flux adjusting block and the base plate facing each other are the same, and whereing said magnetic flux adjusting block becomes closer to the base plate by said bimetallic means when the temperature increases.
 7. A contactless switching device according to claim 4, including a bottom plate formed on the center portion of said U-shaped base is a magnet, the magnetic flux adjusting block comprises a non-magnetized, magnetic material attached on the said base plate, and said magnetic flux adjusting block becomes separated from the base plate by said bimetallic means when the temperature increases. 